[MERGE] Document the new parameter recommend_upgrade of BzrDir.open_workingtree

[John Arbash Meinel]

John Arbash Meinel has voted +1.
Status is now: Approved
Comment:
PING... This still needs to be merged.

There is a small bit of info missing. You have:

... when the workingtree being opened is old (but still fully 
supported).

Maybe "is old" is enough, but to me it is only when we recommend an 
upgrade. For instance we may have --dirstate-with-subtree, but we don't 
recommend upgrading to it over --dirstate.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C1175762904.9221.35.camel%40localhost.localdomain%3E